Origin and course?
The deep fibular nerve is formed by the division of the common fibular nerve (n. fibularis communis). This division occurs within the superior musculoperoneal canal, at a distance of 6–7 cm from the apex of the fibular head.
Further course of the nerve:
- From the lateral compartment, it passes into the anterior compartment by piercing the anterior intermuscular septum of the leg (septum intermusculare anterius cruris) in the upper third of the leg.
- In the leg, the nerve descends along the anterior surface of the interosseous membrane.
- Initially, the nerve lies lateral to the anterior tibial vessels, and in the lower third it shifts to run anterior and medial to them.
- As it passes onto the dorsum of the foot, the nerve lies medial to the artery.
Which muscles does it innervate?
The deep fibular nerve provides motor innervation to the following muscles of the anterior compartment of the leg and the short extensors of the foot:
- Tibialis anterior muscle (m. tibialis anterior) — originates from the lateral condyle of the tibia, interosseous membrane, and crural fascia; inserts into the medial cuneiform and first metatarsal bones. Responsible for dorsiflexion (lifting) and supination of the foot, and supports its arch. Innervated by segments L4–L5.
- Extensor digitorum longus muscle (m. extensor digitorum longus) — originates from the lateral condyle, fibula, and interosseous membrane; attaches to the phalanges of digits II–V. Extends digits II–V; together with the fibularis tertius muscle, pronates the foot (L4–S1).
- Extensor hallucis longus muscle (m. extensor hallucis longus) — originates from the middle third of the fibula and interosseous membrane, attaches to the distal phalanx of the hallux. Extends the big toe, supinates and extends the foot (L4–S1).
- Fibularis tertius muscle (m. peroneus tertius) — often considered part of the extensor digitorum longus. Originates from the distal part of the fibula, attaches to the base of the fifth metatarsal bone. Extends and pronates the foot (L4–S1).
- Short extensors of the toes — receive their motor branch already on the foot, at the level of the intermalleolar line. This branch runs together with the lateral tarsal artery (a. tarsalis lateralis).
What are its cutaneous branches?
The sensory area of the deep fibular nerve is extremely small. On the dorsum of the foot, it provides sensation only to a narrow area between the first and second toes (the first interdigital cleft).
The rest of the skin on the dorsum of the foot is innervated by the superficial fibular nerve (n. fibularis superficialis), and the margins of the foot by the saphenous (n. saphenus) and sural (n. suralis) nerves.
Clinical significance
A lesion of the deep fibular nerve leads to loss of function in the muscles it innervates:
- Paresis (weakness) of the extensors of the foot and toes develops.
- A characteristic clinical syndrome of «foot drop» is formed.
- In mononeuropathy of the fibular nerve not associated with direct trauma or traction, sensory disturbances may also be observed on the dorsal surface of the foot and the lateral surface of the leg.
Class and exam questions
Where does the deep fibular nerve pierce the intermuscular septum?
It pierces the anterior intermuscular septum of the leg (septum intermusculare anterius cruris) in the upper third, passing from the lateral fascial compartment into the anterior one.
How is the nerve positioned relative to the vessels in the leg?
Initially, it lies lateral to the anterior tibial vessels. In the lower third, it shifts anteriorly and medially to them, and on the dorsum of the foot it is also located medial to the artery.
What skin area does this nerve innervate?
The deep fibular nerve provides sensation only to a narrow skin area of the first interdigital cleft (between the first and second toes).
What else to study on this topic
- Common fibular nerve (n. fibularis communis)
- Superficial fibular nerve (n. fibularis superficialis)
- Anterior tibial artery (a. tibialis anterior)
- Muscles of the anterior compartment of the leg
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